The present disclosure generally relates to medical imaging, and more specifically to determining a position of a part of a catheter in a body.
In many applications, including Electro Physiology (EP) applications such as artificial pacemaker implantation, and the diagnosis and treatment of cardiac rhythm disorders, it is required to map the surface of a bodily cavity, i.e., to provide a geometrical description of the surface plane, and to identify the location of one or more blood vessels such as pulmonary veins entering or leaving the cavity.
An artificial pacemaker is a medical device which generates electrical impulses and delivers them by electrodes contacting the heart muscles, to regulate the heart beating. The primary purpose of a pacemaker is to maintain appropriate heart rate. A pacemaker may be required either because the hearts natural pacemaker is not fast enough, or there is a block in the heart's electrical conduction system. Pacemakers may be single, dual or triple chamber, i.e., contain one, two or three leads, respectively. Pacemakers may also include pacing, Implantable Cardioverter Defibrillator (ICD) or Cardiac Resynchronization Therapy (CRT).
Referring now to FIG. 1, showing a schematic illustration of an implanted exemplary pacemaker and its wires. Pacemaker 102 is implanted under the skin in the left upper chest area of the patient. The CRT is delivered as electrical pulses to the right and left ventricles of the heart through soft insulated wires which are inserted through the veins to the heart. The end of each lead is exposed and delivers pulses to the area which it is in contact with. In some applications the pacemaker comprises three leads, wherein end 104 of lead 108 is placed in the right atrium 112, end 116 of second lead 120 is placed in the right ventricle 124, and end 128 of third lead 132 is placed in tissues 136 surrounding left ventricle 140.
In order to place the lead ends so that the signals provide the best possible results, it is required to map parts of the heart, and in particular the right ventricle, so that once a location for the lead end is determined in the right ventricle, the lead can indeed be placed in that location, e.g., on the septum part of the Right Ventricle Outflow Tract (RVOT).
Additional applications that requires mapping of the chambers of the heart relate to mapping the electrical activity of the heart, including creating maps showing the relative timing of the electrical activities at different parts of the heart. Sometime mapping and treatment requires going through the septum between the right atrium to the left atrium mapping the right atrium may provide guidance for passing transseptally into the left atrium. In the left atrium the location of the pulmonary veins is of interest for many procedures both for diagnostic and for treatment purposes.
Some methods are known in the heart for mapping cavities, such as heart ventricles. One family of methods includes a 3-dimensional electromagnetic mapping system, which comprises one or more electromagnetic location pads positioned externally to the patient, and an electromagnetic sensor-equipped catheter. At each point the catheter provides its location according to the sensed magnetic field.
Another family of methods includes attaching three pairs of electrodes to the patient, wherein each pair is orthogonal to the other two pairs of electrodes, so as to cover the 3-dimensional space.
A mapping catheter is inserted into the body of a subject and placed adjacent to the mapped feature. The Voltage measured by the mapping catheter indicates the location of the measuring electrode along the dimension of the line connecting each pair of electrodes, which enables the determination of the three dimensional location of the measuring electrode.
However, each of these methods requires special equipment and procedures which are generally not available in operating rooms.
There is thus a need in the art for a method and apparatus for mapping bodily cavities with standard equipment available in operating rooms, and in particular X-ray imaging equipment. Although X-ray equipment provides two-dimensional images, yet it is required to obtain a three-dimensional mapping of the cavity such as a heart ventricle, by mapping an external surface thereof.